Neurophysiological Effects on tPCS and tDCS on Healthy Subjects and on Patients With Chronic Visceral Pain

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12 out of the 48 total health subjects will receive active tPCS and active tDCS. This will be done for 20 minutes simultaneously.

Device: Active tPCS

A current intensity of 2mA and a stimulation frequency range of 6-10 Hz will be used with a peri-aurical ear-clip electrode montage for 20 minutes.

Device: Active tDCS

A current intensity of 2.0 mA will be used for 20 minutes. The electrodes that will be used will be standard sponge electrodes. The anode will be placed over left motor cortex. The cathode electrode will be placed over the contralateral supraorbitofrontal area.

Experimental: Part 1: Active tPCS, Sham tDCS

12 out of the 48 total health subjects will receive active tPCS and sham tDCS. This will be done for 20 minutes simultaneously.

Device: Active tPCS

A current intensity of 2mA and a stimulation frequency range of 6-10 Hz will be used with a peri-aurical ear-clip electrode montage for 20 minutes.

Device: Sham tDCS

Sham tDCS stimulation will consist of applying the same parameters as for active, but the corresponding device will be turned off after 30 seconds, as to simulate the initial sensation of the active current. A current intensity of 2.0 mA will still be used (but turned off after 30 seconds using ramping). The electrodes that will be used will be same, standard sponge electrodes. The anode will be placed over the left motor cortex The cathode electrode will be placed over the contralateral supraorbitofrontal area.

Experimental: Part 1:Sham tPCS, Active tDCS

12 out of the 48 total health subjects will receive sham tPCS and active tDCS. This will be done for 20 minutes simultaneously.

Device: Active tDCS

A current intensity of 2.0 mA will be used for 20 minutes. The electrodes that will be used will be standard sponge electrodes. The anode will be placed over left motor cortex. The cathode electrode will be placed over the contralateral supraorbitofrontal area.

Device: Sham tPCS

Sham tPCS stimulation will consist of applying the same parameters as for active, but the corresponding device will be turned off after 30 seconds, as to simulate the initial sensation of the active current. A current intensity of 2mA and a stimulation frequency range of 6-10 Hz will still be used (only this will be turned off after 30 seconds using ramping) with a peri-aurical ear-clip electrode montage.

Sham Comparator: Part 1: Sham tDCS, Sham tDCS

12 out of the 48 total health subjects will receive sham tPCS and sham tDCS. This will be done for 20 minutes simultaneously.

Device: Sham tPCS

Sham tPCS stimulation will consist of applying the same parameters as for active, but the corresponding device will be turned off after 30 seconds, as to simulate the initial sensation of the active current. A current intensity of 2mA and a stimulation frequency range of 6-10 Hz will still be used (only this will be turned off after 30 seconds using ramping) with a peri-aurical ear-clip electrode montage.

Device: Sham tDCS

Sham tDCS stimulation will consist of applying the same parameters as for active, but the corresponding device will be turned off after 30 seconds, as to simulate the initial sensation of the active current. A current intensity of 2.0 mA will still be used (but turned off after 30 seconds using ramping). The electrodes that will be used will be same, standard sponge electrodes. The anode will be placed over the left motor cortex The cathode electrode will be placed over the contralateral supraorbitofrontal area.

Experimental: Part 2: Active tPCS/Active tDCS

Part 2 will run as a four-period crossover design, where all chronic visceral pain subjects (18 total) will be receiving all (4) possible combinations of tDCS and tPCS interventions (active or sham) at the end of the experiment in a random, consecutive way. This represents the combination of receiving active tPCS and active tDCS (1/4 combinations all subjects will receive).

Device: Active tPCS

A current intensity of 2mA and a stimulation frequency range of 6-10 Hz will be used with a peri-aurical ear-clip electrode montage for 20 minutes.

Device: Active tDCS

A current intensity of 2.0 mA will be used for 20 minutes. The electrodes that will be used will be standard sponge electrodes. The anode will be placed over left motor cortex. The cathode electrode will be placed over the contralateral supraorbitofrontal area.

Experimental: Part 2: Active tPCS/Sham tDCS

Part 2 will run as a four-period crossover design, where all chronic visceral pain subjects (18 total) will be receiving all (4) possible combinations of tDCS and tPCS interventions (active or sham) at the end of the experiment in a random, consecutive way. This represents the combination of receiving active tPCS and sham tDCS (1/4 combinations all subjects will receive).

Device: Active tPCS

A current intensity of 2mA and a stimulation frequency range of 6-10 Hz will be used with a peri-aurical ear-clip electrode montage for 20 minutes.

Device: Sham tDCS

Sham tDCS stimulation will consist of applying the same parameters as for active, but the corresponding device will be turned off after 30 seconds, as to simulate the initial sensation of the active current. A current intensity of 2.0 mA will still be used (but turned off after 30 seconds using ramping). The electrodes that will be used will be same, standard sponge electrodes. The anode will be placed over the left motor cortex The cathode electrode will be placed over the contralateral supraorbitofrontal area.

Experimental: Part 2: Sham tPCS/Active tDCS

Part 2 will run as a four-period crossover design, where all chronic visceral pain subjects (18 total) will be receiving all (4) possible combinations of tDCS and tPCS interventions (active or sham) at the end of the experiment in a random, consecutive way. This represents the combination of receiving sham tPCS and active tDCS (1/4 combinations all subjects will receive).

Device: Active tDCS

A current intensity of 2.0 mA will be used for 20 minutes. The electrodes that will be used will be standard sponge electrodes. The anode will be placed over left motor cortex. The cathode electrode will be placed over the contralateral supraorbitofrontal area.

Device: Sham tPCS

Sham tPCS stimulation will consist of applying the same parameters as for active, but the corresponding device will be turned off after 30 seconds, as to simulate the initial sensation of the active current. A current intensity of 2mA and a stimulation frequency range of 6-10 Hz will still be used (only this will be turned off after 30 seconds using ramping) with a peri-aurical ear-clip electrode montage.

Sham Comparator: 2: Sham tPCS/Sham tDCS

Part 2 will run as a four-period crossover design, where all chronic visceral pain subjects (18 total) will be receiving all (4) possible combinations of tDCS and tPCS interventions (active or sham) at the end of the experiment in a random, consecutive way. This represents the combination of receiving sham tPCS and sham tDCS (1/4 combinations all subjects will receive).

Device: Sham tPCS

Sham tPCS stimulation will consist of applying the same parameters as for active, but the corresponding device will be turned off after 30 seconds, as to simulate the initial sensation of the active current. A current intensity of 2mA and a stimulation frequency range of 6-10 Hz will still be used (only this will be turned off after 30 seconds using ramping) with a peri-aurical ear-clip electrode montage.

Device: Sham tDCS

Sham tDCS stimulation will consist of applying the same parameters as for active, but the corresponding device will be turned off after 30 seconds, as to simulate the initial sensation of the active current. A current intensity of 2.0 mA will still be used (but turned off after 30 seconds using ramping). The electrodes that will be used will be same, standard sponge electrodes. The anode will be placed over the left motor cortex The cathode electrode will be placed over the contralateral supraorbitofrontal area.

Signal Coherence and EEG power as measured Quantitative Electroencephalographic Analysis (qEEG): [ Time Frame: For the healthy subjects during their 1-time study visit; For visceral pain patients, it will be measured over the course of about 3 weeks ]

The EEG test is performed to measure the electrical activity in the brain and to examine the dynamic changes.

Secondary Outcome Measures :

Pressure Values as measured by Pain Pressure Test (PPT) for Conditioned Pain Modulation (CPM) [ Time Frame: For the healthy subjects during their 1-time study visit; For visceral pain subjects, it will be measured over the course of about 3 weeks ]

These procedures incorporate a conditioning stimulus (a noxious stimulus that evokes Descending Noxious Inhibitory Control (DNIC) activation) and a test stimulus (a noxious stimulus used to evaluate the analgesic response to the conditioning stimulus- this will be the PPT as determined by an algometer (JTECH medical)). This study will evaluate CPM in healthy subjects as well as in patients with chronic visceral pain using pressure as the test stimulus, and cold water as the conditioning stimulus.

Sensitivity of Filaments as measured by Von Frey assessment [ Time Frame: Only done for visceral pain subjects; it will be measured over the course of about 3 weeks. ]

This assessment will be performed before and after every intervention on a patient with pain. Mechanical perception and pain threshold will be tested on the painful region and on other non-painful area Von Frey monofilaments (0.4 g to 50 g) (these are fine filaments that can test a subject's perception threshold when they are applied to the body surface). Monofilament application will be applied to the painful region and a non painful region on the same side of the body (i. e. left or right). The hairs will be applied until subject perceives the stimulus (perception threshold) and describes it as painful (pain threshold). The threshold will be taken as the lowest force that causes pain perception in the affected and contralateral mirror healthy site.

Pain score as measured by Visual Analogue Scale (VAS) for Pain: [ Time Frame: Only done for visceral pain subjects; it will be measured over the course of about 3 weeks. ]

The VAS is a self-reporting test asking subjects to self-measure their pain on a visual scale from zero to ten (i.e., none to unbearable). This will help us monitor changes in subjects' pain levels when they come in for sessions.

Pain levels and medication intake as measured Pain/Medication Diary [ Time Frame: Only done for visceral pain subjects; it will be measured over the course of about 3 weeks ]

To monitor pain levels, as well as safety, patients with chronic visceral pain will keep a diary listing their daily medications and pain levels when not at the laboratory.

Mood scores as measured Visual Analog Mood Scale (VAMS) [ Time Frame: Only done for visceral pain subjects; it will be measured over the course of about 3 weeks ]

This is a self-reporting assessment in which subjects rate their own emotions, including anxiety, depression, stress, and sleepiness along a 100mm line.

A 21-item, multiple-choice questionnaire will be administered at the beginning of the study to all subjects to assess the presence and degree of depression in adults, as studies in chronic pain have found that depression can modulate pain perception.

Effectiveness of blinding as measured by the tPCS and tDCS Blinding Questionnaire [ Time Frame: For the healthy subjects during their 1-time study visit; For visceral pain subjects, it will be measured over the course of about 3 weeks ]

After the stimulation session, subjects will complete a questionnaire to determine if the blinding methods were effective. A 30s sham montage is used,which is consistent with other trials, keeping the device on the subject for the duration of the session.

Side-effects from stimulation as measured by the tDCS and tPCS Side Effects Questionnaire [ Time Frame: For the healthy subjects during their 1-time study visit; For visceral pain subjects, it will be measured over the course of about 3 weeks ]

At the end of each stimulation session, subjects will complete a questionnaire to evaluate potential side effects of stimulation (headache, neck pain, mood alterations, and seizures) on a 5-point scale. Subjects will be asked whether they have experienced any side effects in open-ended questions. They will also be specifically asked about headache, neck pain, scalp pain, scalp burns, tingling, skin redness, sleepiness, trouble concentrating, and acute mood change. If any side effects are reported, the degree of relatedness to the intervention will be assessed.This assessment identifies adverse effects using open-ended questions.

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Layout table for eligibility information

Ages Eligible for Study:

18 Years to 60 Years (Adult)

Sexes Eligible for Study:

All

Accepts Healthy Volunteers:

Yes

Criteria

PART 1: 48 healthy subjects will be selected to take part in this study. All healthy subjects will need to meet all of the following inclusion criteria and none of the following exclusion criteria:

Inclusion criteria:

Provide informed consent to participate in the study

Age 18 - 60 years

Exclusion criteria:

History of alcohol or substance abuse within the last 6 months as self-reported

Severe depression (with a score of >30 in the Beck Depression Inventory)*

History of seizures during the last two years or diagnosis of epilepsy